Re: Do we live forever that we can afford to waste time Posted on: Fri May 14, 2010 6:50 pm

Dan, I just had a look at your car project at the link above, as well as the rest of the site. First, I underestimated you somewhat I think, for which I'm sorry. You come across as one of the many armchair technologists who know it all, but never actually build something. You do have some finished projects on your site. Kudos for that.

I have a few questions about the project.

For one, won't putting 1000A into the motors simply set them on fire, rather than accelerating you at Ferrari speeds? After all, that's 80kW at 80V, over 100hp. That's way above any rating I can find for your motor (15 hp max and 8 hp continuous, and 150A under load; even spread across two motors that's 300% the rated maximum).

Second, at what average speed and driving conditions (e.g. freeway, urban) do you calculate the 100 km range? At 3 kWh of stored energy, 80V and 1kA you're going to empty the batteries in a little more than two minutes, which won't be enough to drive 100 km. At 5kW (about 90% of the rated 8 hp) power consumption you're out of fuel in a bit over half an hour, so you'd have to drive quite a bit faster than your stated maximum of 140 km/h. My present commute is around 23 km, which I do by bicycle, train (electric on "green" electricity, so already carbon neutral) and again bicycle in 40 minutes. How quickly could I do it with the Freeranger?

Third, wouldn't it be more cost-effective to just buy one of these (or a newer similar vehicle, this one is from 2008 it seems and technology is moving fast) and use the parts? After all it's a prototype.

Fourth, one of the reasons people drive SUVs is that it makes them feel more safe, being sat high in a massive vehicle. For sure, driving something as flimsy as the Freeranger in traffic seems a bit scary to me. Less emotionally and more legally speaking, how are you going to make it survive the required crash tests to make it street-legal? It seems that what would be a relatively minor accident without personal injuries in an ordinary car would result in at least a few broken limbs if you're driving the Freeranger.

Last (for now ), how is the Freeranger different from a typical Eco-marathon car?

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Re: Do we live forever that we can afford to waste time Posted on: Fri May 14, 2010 11:12 pm

Lourens wrote:

I have a few questions about the project.

Dan will solve all these problems by speaking to the freeranger in a very stern and condescending manner. If you think the way he speaks on this forum is obnoxious, you ain't seen nothing yet. He is just using us to hone his belligerence skills. And you seem to have forgotten that God is on his side as a backup, just in case the power of attitude isn't as effective as his calculations predict.If Dan would sue Steve Jobs for stealing the Reality Distortion Field that Dan originally invented many decades ago, I'm sure he would get enough damages from the court to finance all his projects.

Re: Do we live forever that we can afford to waste time Posted on: Sat May 15, 2010 1:24 am

Lourens, apology accepted.A lot of the questions you could probably answer yourself. the quetions are fine but you can take that step further and think about how it could work.

iirc the working parameters are 300 Ampere into each motor at peak acceleration. at 100V that's 40 HP each. they should be able to handle 300A for a while.

the range should be at around 100km/h and of course not at maximum power output. (bugatti veyron runs dry after 12minutes at full power). it is based on estimates. I don't have aerodynamics data on it. there is a lack of easy to use computational wind tunnel sofware in this world.

I didn't design the vehicle to be the cheapest way I could become mobile. some second hand scooter could do that. it's designed to be a very practical ultra efficient vehicle for the masses to use and it's layout is critical functional element. there is not a lot to reuse from the vehicle you linked.

people drive SUVs because they are sheep and do as they are told. but it's true that something as light as the freeranger concept has a substantial disadvantage in a head on crash. you can actually make it quite strong but there is no way around the mass disadvantage which decides the resulting speed change in head on collision. a 200kg vehicle against a 3000kg moronic suburban is a losing prospect but there are two aspects to that, one, should we all drive 70 ton tanks because a mere 40 ton tank is unsafe? and two, being an early adopter is in this instance a sacrifice of risk because it's the right thing to do and all vehicles should be much lighter. a 3 ton suburban will of course not help you when banging into a concrete pillar.dumbass tiger woods knocked himself out at a walking pace in such a car.

the concept is naturally similar to eco racers because the premise is similar but if you actually look at the shell eco 'urban' cars they are typically very tiny cabins for a single person lying flat on his back a few cm above the ground. the freeranger is about as tall as a porsche with a comfortably large cabin sitting almost upright and room for two plus trunk/boot for a set of golf clubs. dimensions much like a porsche but spear body and disc wheels and scooter weight makes it consume 20 times less energy while easily outaccelerating the old obese crude porsche

all that jersey shore loud wruum wruum and nothing to show for it.it is literally easy to make an EV do 0-100km/h in 1.5seconds if only the wheels are soft enough to grip that.and don't think of it as flimsy. fiber glass or carbon can be made very strong with very little weight.

think about it.

similarly lean design can be applied to 4 seater cars. easily beat porsches with inexpensive design. power electronics is surprisingly cheap, batteries can be very powerful and electric motors are cheakily willing to do great power for the 8 seconds it takes to make a veyron owner cry.

John Carmack has a tesla roadster which has quite decent performance but that's a marathon car with a very heavy battery pack of very low power cells. it's a 1200kg car with only about 170kW power. a 2 seater roadster type car can easily weigh less than 700kg if done right with a 200kg battery pack that can deliver 800kW. even if we settle for a 450kW motor to avoid cascade weight buildup, it's still gonna move it will make a veyron look like it's standing still on a quarter mile.here's a 700kg EV with only 150kW power: http://www.youtube.com/watch?v=8qDZOBQs60w (you can skip to 1:30 to see the action) it does ok.

and I know what I'm talking about. please don't indulge urges to kneejerk object to the things I've said.

Re: Do we live forever that we can afford to waste time Posted on: Sun May 16, 2010 10:26 pm

Dan Frederiksen wrote:

Lourens, apology accepted.A lot of the questions you could probably answer yourself. the quetions are fine but you can take that step further and think about how it could work.

I'm sorry, given your confidence in the design I was under the impression that you had done the calculations, and could easily give a bit more information and some numbers. I'm a computer scientist, not a mechanical or electrical engineer, and I'm certainly no genius, but I will give it a go.

Quote:

iirc the working parameters are 300 Ampere into each motor at peak acceleration. at 100V that's 40 HP each. they should be able to handle 300A for a while.

I did search for an official datasheet of some kind, but was unable to find anything quickly on the web. I did find afewsites giving numbers, 8 hp continuous and 15 hp max, or 2.7 hp continuous and 12 hp max. I'm not sure if that is the exact same model you have, and later models would likely be more powerful as the design gets optimised, but it's quite a bit less than the 40 hp you mention.

The second link does list 300A for 30s, but also gives a 50V (nominal?) voltage, not 100V. That would make for 15kW, or about 20 hp. Given the above maximum of 15 hp, it seems most likely to me that that 300A for 30s is a safety limit, i.e., it won't catch fire for at least 30s if you put in 15 kW. Of course, it will depend on your cooling arrangements as well, but the Freeranger does not have water cooling, and if it's accelerating from a standstill then there won't be much air cooling either.

However, even at 2 x 15 hp it's probably going to accelerate plenty fast. I don't think anyone questions the acceleration ability of an electric car, especially if it's as light as the Freeranger.

Quote:

the range should be at around 100km/h and of course not at maximum power output. (bugatti veyron runs dry after 12minutes at full power). it is based on estimates. I don't have aerodynamics data on it. there is a lack of easy to use computational wind tunnel sofware in this world.

Wasn't there someone on the board here who was working on some CFD software? I think he had a model of Scorpius in it. Might not be too difficult to put in the Freerider and see if you can get some ballpark figures.

Quote:

I didn't design the vehicle to be the cheapest way I could become mobile. some second hand scooter could do that. it's designed to be a very practical ultra efficient vehicle for the masses to use and it's layout is critical functional element. there is not a lot to reuse from the vehicle you linked.

I was thinking the motor, batteries and electronics? Or am I mistaken in that the technologies used are similar?

Quote:

people drive SUVs because they are sheep and do as they are told. but it's true that something as light as the freeranger concept has a substantial disadvantage in a head on crash. you can actually make it quite strong but there is no way around the mass disadvantage which decides the resulting speed change in head on collision. a 200kg vehicle against a 3000kg moronic suburban is a losing prospect but there are two aspects to that, one, should we all drive 70 ton tanks because a mere 40 ton tank is unsafe? and two, being an early adopter is in this instance a sacrifice of risk because it's the right thing to do and all vehicles should be much lighter. a 3 ton suburban will of course not help you when banging into a concrete pillar.

There's a lot of hyperbole here. I agree that part of the problem is SUVs, and they do endanger anyone driving something smaller, but even without any other cars, parking a Freeranger into a tree at 100 km/h is still uncomfortably close to what happens if your parachute fails to open when skydiving. Or what about being hit from the side by another Freeranger that ran a red light, at 50 km/h? The fast acceleration also means that anyone not paying attention when pulling away from a stop will hit someone close by at higher speed.

Quote:

the concept is naturally similar to eco racers because the premise is similar but if you actually look at the shell eco 'urban' cars they are typically very tiny cabins for a single person lying flat on his back a few cm above the ground. the freeranger is about as tall as a porsche with a comfortably large cabin sitting almost upright and room for two plus trunk/boot for a set of golf clubs. dimensions much like a porsche but spear body and disc wheels and scooter weight makes it consume 20 times less energy while easily outaccelerating the old obese crude porsche

Your pictures (they're nice by the way, is that polygon-rendering (with radiosity?) or raytracing? What modeller do you use?) don't show the dimensions, but I'm a bit worried about the way I'm supposed to wrap my legs around the driver when sitting in the back seat. I'm 1.90, will I still fit? And will I be able to change posture once in a while to avoid cramps on longer drives?

Quote:

all that jersey shore loud wruum wruum and nothing to show for it.it is literally easy to make an EV do 0-100km/h in 1.5seconds if only the wheels are soft enough to grip that.

Again, I'm not worried about the acceleration. I'm more worried about top speed and range, and a bit about reliability.

This page lists the Cd of the Nuna Solar Car as 0.07. The Freeranger doesn't have covered wheels, which probably matters quite a bit, but it's also probably more aerodynamic than an ordinary car. Perhaps Cd = 0.15? The power required to overcome air resistance is (according to Wikipedia)

Pd = Fd * V = 1/2 * rho * v^3 * A * Cd

The frontal area of the Freeranger will be bigger than that of Nuna (0.86 m^2 according to the above link) due to the more upright position, let's say 1.2 m^2?. rho, the air density, is about 1.2 kg/m^3 on a nice day in The Netherlands, and we have 16 hp or 12 kW of power sustained. That will give

Your total weight goal is 100 kg + 30 kg batteries, and add two warmly dressed Lourenses (155 kg) and some groceries (15 kg) for a total normal force Fn of 2.9 kN. A racing bike tyre has a Cr of about 0.003, so at 48 m/s

Pr = 0.003 * 2.9 kN * 48 m/s = 0.42 kW

That's about 3.5%, so your 140 km/h top speed is probably realistic.

So let's look at range. Your battery would hold about 3 kWh, or about 10MJ (rounding down from 10.8, since it was a bit less than 3kWh anyway, and it won't always be in pristine condition, plus draining it completely is probably a bad idea). Given a perfectly efficient engine, you could ride at top speed for

1.0 * 10^7 J / 1.2 * 10^4 W = 8.3 * 10^2s or about 14 minutes

The second link about the engine gives 3200 rpm and 150 A at a torque of 160 lbin = 18 Nm (it says lbln, I assume that's a typo). At the 50V nominal voltage, that's 7.5 kW (10 hp) electrical power input and 3200 * 18 / 60 = 0.96 kW mechanical power output. That's a rediculously low efficiency though, so I must be missing something. Can you help me out here?

From looking around a bit, 95-98% efficiency seems more common for electric motors, so that's not going to affect our order of magnitude much. I'm not sure about drive train losses, but it's getting late, so I'll leave that for some other time.

Let's get back to my commute and look at speeds for a bit. One important factor I've not taken into account is having to accelerate and decelerate in urban traffic all the time, and having to go up and down bridges in Amsterdam. According to the EPA, the Toyota RAV4 electric vehicle does 29 (mpg?) in the city and 37 (mpg?) on the highway. My commute is about 50/50, so I'm going to put in a 0.9 penalty factor for that. European cities are probably worse than US cities due to them being smaller, but then the Freeranger is lighter too.

Let's say that I need a range of 50 km for my commute. Total power is

P = Pd + Pr = 1/2 * rho * v^3 * A * Cd + Cr * Fn * v

and we can multiply that by driving time t to get the total amount of energy used and equate it to the battery contents:

That's pretty impressive; I could probably do my commute with a Freeranger. The same equation gives an average speed of 28 m/s or 100 km/h for a range of 100 km.

Of course, the above is one assumption on top of the other, and it remains to be seen whether the Freeranger design can be built (let alone mass-produced), but it does provide some support for your guesses. It could be improved a lot with better specs on the motor and a good estimate of the Cd.

Incidentally, looking at the specs and intended use, you could see this as an electric 2CV .

Quote:

and don't think of it as flimsy. fiber glass or carbon can be made very strong with very little weight.

I remember a driver (was it Robert Kubica?) putting his F1 car into a concrete wall at something like 200 km/h a few years ago, and getting away with a bruised ankle. But F1 drivers are very well trained athletes with lots of muscles, and more importantly, they're strapped tight inside a carbon fibre monocoque wearing helmets and neck support, rather than sitting on top of a fibreglass plate in shirtsleeves. Also, the minimum dry weight of an F1 car is something like 600 kg IIRC. So I'm not sure that that says anything about the safety of the Freeranger.

Personally, I found the Smart two-seater pretty scary on the highway. I don't think I'd happily drive a Freeranger at 100km/h.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Re: Do we live forever that we can afford to waste time Posted on: Mon May 17, 2010 1:41 am

Lourens, it's not a 2CV : )

you can increase voltage in a motor without heat issues. voltage is related to spin rate. as long as it doesn't spin too fast to hold together basically.

it was designed for a particular impressive power level. the scooter parts wouldn't do.

electric motors are not typically 95-98% efficient. DC often as low as 85% at their best although in part due to sloppy industrial design.the etek motors I chose are not really suited either. I realized later that their efficiency is only decent at high power levels and rather bad in a cruise. so a commercial model would have to use different motors. not technically dificult though, just not that particular product.

there was no hyperbole in what I said. that's just you still resisting the idea without reason

and if you run into a tree at 100km/h in any car you generally die. iirc statistics show that fatality rates rise to 100% very quickly just around 100km/h head on. a light car that is properly designed is only at a disadvantage against a heavier car, not an immovable object.a foam car would suffice.

as you yourself realized but are reluctant to admit, a fiber composite structure can be plenty safe as in formula 1. although when they survive 200km/h crash it is either soft targets or at a shallow angle. a fiber car could remain largely intact after a 200km/h impact with immovable obstacle but the driver would not.

you would be less concerned with a light vehicle if the stupid SUVs were no longer legal and 4 seater cars weighed 600kg.

Re: Do we live forever that we can afford to waste time Posted on: Mon May 17, 2010 8:34 am

Well, the 2CV was intended for short trips from the farm to the market, which is sort of a commute. It's light and low power. The way I see it, the main difference is that the Freeranger isn't much good on a bumpy muddy country road.

I know that P = I^2 * R for a simple resistor, but I'm not sure how that changes for inductive loads and loaded motors. We would have to know how much current the motor draws at 100V and the given load to be able to do a better computation I guess.

Referring to an SUV as a 70-ton tank is hyperbole. Either that or misinformed, and since you gave an accurate 3 ton as well, I don't think you're misinformed.

As for safety, most cars have crumple zones to take up part of the impact energy. F1 cars completely disintegrate if you crash them at high speed. They're designed to do that, because it is the most efficient way of dissipating the energy of the collision. The point isn't to keep the car intact, it's to sacrifice the car and keep the driver intact. Incidentally, there's an interesting article on safety and speed here. It says 50% chance of fatality at 60 mph, in 1993. It's also interesting to compare that to the earlier study also given there, from 1982. Assuming cars have kept getting safer, a 100 km/h crash will still be very dangerous, but not an automatic fatality. I surmise that crumple-zone-wise, the Freeranger is more similar to an 80's car than to a modern one.

You also didn't address my argument why an F1 car is different (and less safe) than the Freeranger. I've been giving a lot of research and arguments here. The point where you will have to start responding in kind is approaching I'd say.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Re: Do we live forever that we can afford to waste time Posted on: Mon May 17, 2010 9:16 am

Part of the 'problem' with modern car regulations is the safety requirements. The reasons that fuel economy hasn't changed all that much over the last ten years is that advances in engine efficiency have been offset by increased safety requirements, which always mean more weight, which of course hampers efficiency. This is a realt ough one to get round. As stated above, carbon fibre monocoques as used in F1 and other race series are extremely strong, and keep the occupant safe in very high speed crashes. However, it is very very expensive, and the fact you only have one occupants makes the design easier. It will be very difficult to make a fully carbon car, to safety regs, for two or more people, that is affordable by the general populace. It will come I am sure, but its too expensive AT THE MOMENT.

I have had some pretty big crashes in the car in my avatar picture - that is a steel spaceframe (85mph sideways in to armco). The only reason I came out 'unhurt' is very very good seat belts. So it can be done in steel/ali, but that is heavy - my race cars weighs about 600kg including driver.

But, batteries are also heavy. I am more of a fan of a gas turbine powered car - turbine->generator->electricity->super capacitor->in wheel motors. This provides the ability to run the turbine at its highest efficiency at all times. The super capacitor provides for regenerative braking capacity (or you could use a mechanical system like the Williams F1 team developed).

Re: Do we live forever that we can afford to waste time Posted on: Mon May 17, 2010 11:35 am

Lourens, sighmaybe the freeranger has slightly better acceleration than the 2CV..maybe slightly better energy efficiency..I didn't refer to an SUV as a 70 ton tank. read it again

when did you argue that a formula 1 car is less safe than the freeranger?if you mean the other way around, then try to realize the shape of the freeranger is a lot like a formula 1 car and can of course employ the same safety design or better. higher weight is not a simple advantage. that's just more weight you have to stop as well.I'm not going to answer you again unless you own up and stop your massive mistakes.

JamesHughes, safety requirements has nothing to do with the weight gain. that's a common misconception invoked to avoid realizing the truth.battery drive is vastly superior to anything else although generators will have a role as range extenders to overcome the one critical weakness of batteries, total capacity. a turbine might serve as such but not yet clear if a small one can be made light, powerful and efficient enough. capstone has promoted their turbines for car use but their specs suck.

Re: Do we live forever that we can afford to waste time Posted on: Mon May 17, 2010 12:31 pm

Dan Frederiksen wrote:

you can increase voltage in a motor without heat issues. voltage is related to spin rate. as long as it doesn't spin too fast to hold together basically.

You are wrong on so many levels there it isnt even funny. You obviously have very little knowledge about electrical systems. While I give Lourens props for trying to run through the numbers, I will not indulge you Dan.

I say 'Try' because it sounds like you provide only very very vague specs other than a 'dream sheet' of what you want to get out of it. Bad engineering practices is all that it screams to me. This in turn tells me to back away, and not touch this unsafe design anymore.

Dan Frederiksen wrote:

capstone has promoted their turbines for car use but their specs suck

Dan... from what i've come to know about you, anything that isn't your idea sucks.

@johno,JamesHughes: I've liked the microturbine as a generator for a while myself, Had done a bit of research into them for a power generation concept.Still leaning towards doing a diesel-electric conversion on an 18-wheeler one of these days. That'd be a sweet sweet market here Stateside. Just look at the Diesel-lectrics on the Railroads. While massive, the power and efficiency of the system is impressive.

I used to like the thought of wheel motors, but after reading one article, I was convinced otherwise. I'll have to try and dig it up to share. The gist being that hub motors are great for small applications, though when higher power requirements and a larger perfromance band (slow speed, high torque to high speed lower torque or city vs highway) its not the best choice. I still like Regen braking though

Batteries will still be an issue. From what I can tell, the only company to produce a worthwhile EV battery is A123 systems. Heck look what they did with a drag bike http://en.wikipedia.org/wiki/Killacyclethose figures are apparently a little out of date, but the point being that these Batts have a serious discharge rate.company website: http://www.a123systems.com/

On a different topic: Anyone here ever experiment with Hybrid rockets?